The use of concrete mixer trucks is known, which using a rotating drum transport concrete from a production plant to the building site where the concrete is used.
Both during the loading step in the production plant, and during the transport step to the building site, the concrete has to be kept malleable, and so the rotating drum has to be kept in constant rotation so that the concrete does not harden.
It is known that, upon arrival at the building site, the mixer truck sometimes has to wait its turn to unload. During this waiting step too, the drum has to be kept in constant rotation.
It is also known that before the unloading step, the concrete undergoes a homogenization step, and to achieve this the drum of the mixer truck is made to turn at its maximum rotation speed.
It is also known that during the unloading of the concrete, the drum is made to rotate in the opposite direction to the mixing direction.
In known concrete mixer trucks, the rotation of the drum is normally achieved by means of a hydraulic motor, which is driven by a group of pumps made to rotate by a heat engine which is usually a diesel engine. The heat engine can also be the same one that moves the vehicle or it can be an independent auxiliary heat engine.
One considerable disadvantage of known concrete mixer trucks is that the heat engine, whether it is the only one which moves the vehicle, or whether it is both the above cited heat engines, in the place where the concrete mixer truck is loaded and at the building site, one or both must be kept functioning, both to move the mixer truck and to rotate the drum.
It is also known that heavy vehicles, such as concrete mixer trucks, as well as being a source of noise also emit noxious gases from the heat engines.
From documents JP-A-2003/226192, JP-A-2003/301802, and from document DE-U-20 2009 001416, a solution is known whereby the rotating drum of the concrete mixer truck is driven with the aid of an electric motor.
In particular document JP-A-2003/226192 describes a concrete mixer truck provided with a rotating drum directly connected by means of reduction members to the electric motor. The electric motor is fed, depending on the functioning conditions, either by an electric energy generator driven directly by the heat engine of the concrete mixer truck, or by batteries that accumulate electric energy.
This solution is limited, however, in that it has a reduced operating flexibility due mainly to the univocal power, entrusted each time only to the generator or only to the accumulation batteries, with a subsequent reduction in functioning autonomy.
US 2009/095549 A1 describes an energy generation system for a hybrid vehicle in which there is a power take-off (PTO) connected to the main engine of the vehicle, a source of rechargeable electric power, a hydraulic motor in direct or indirect mechanical communication with the power take-off and an electric motor in direct or indirect communication with the hydraulic motor.
In this document no alternative sources to recharge the electric power source are provided. Moreover, the presence of a hydraulic motor is in any case required.
In a patent application filed by Applicant on 26 Jan. 2012 under MI2012A000093, a solution is described based on which it is possible to move the rotating drum with accumulated energy and transformed into high-efficiency electric energy, with high electric yield; this solution guarantees considerable practicality and operating flexibility. Indeed it has different sources to generate or accumulate electric energy and also provides the synergic use of these sources to increase the functioning autonomy of the rotating drum.
Starting from this solution, in itself extremely efficient and flexible, Applicant has further developed the concept on which the auxiliary device that feeds the concrete drum is based, to achieve a situation in which the noxious gases released by the mixer truck are nearly non-existent at least in circumstances other than long transfers.
Another disadvantage faced is to provide an almost total reduction of the noise produced by the concrete mixer trucks during their own movement, on the road or in the areas of work.
One purpose of the present invention is therefore to obtain a concrete mixer truck equipped with an auxiliary device of the electric type, perfected with respect to that described in application MI'093, but which is able to simultaneously move, at least for a certain period, both the rotating drum and also the mean of transport or vehicle which transports it.
One purpose of the present invention is also to obtain a concrete mixer truck that can be moved by exclusively electric or electromechanical means, without requiring an application of the hydraulic type as provided for example in document JP-A-2003/301802 or US 2009/0095549, in order to drive the drum.
Another purpose of the present invention is to obtain a concrete mixer truck provided with electric means to actuate the rotating drum and to move the concrete mixer truck itself which are efficient, flexible, and which allow to obtain great functioning autonomy.
Another purpose of the present invention is to obtain a concrete mixer truck provided with an auxiliary device able to drive the mixing drum and to move the vehicle on which it is mounted, while keeping the heat engine or engines with which the concrete mixer truck is provided switched off during these operations.
It is however important to safeguard the health of the persons who are near the concrete mixer truck, including the operators in the loading site and in the building sites involved.
The invention thus sets itself the purpose of at least greatly reducing the emission of noxious gases both in the work places and in city areas, for example subject to traffic limitations or during restricted noise emission hours.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.